Raytheon Co. has appointed Sue Baumgarten as president of Raytheon International Inc. She replaces Hansel Tookes, who is retiring.   . . .   Brashear LP has selected Three-Five Systems' Brillian Z86D-3 microdisplays to be the primary display in the XM29, an advanced weapon for US ground troops. Three-Five will provide Brashear with SVGA microdisplays, ASICs and optics and illumination consultation for the target acquisition and fire control aiming system in the XM29.